code: def __call__(self, a):
      shape = list(a.shape)
      shape[self.axis] -= self.n
      shape = tuple(shape)
      return self.new_tensor([a], shape, dtype=a.dtype, order=a.order)
  
file_path: mars/mars/tensor/base/diff.py
imports: from ...serialization.serializables import Int64Field, Int32Field
  from ...core import recursive_tile
  from ..operands import TensorOperand, TensorOperandMixin
  from ..utils import validate_axis
  from ..datasource import tensor
label_desc: Use image node_id 1 for calling the TensorDiff obj's underlying member method code with example usage: obj.__call__(a) and returns: self